1. Field
Apparatuses and methods consistent with exemplary embodiments relate to a receiver and a decoding method thereof, and more particularly, to a receiver and a decoding method thereof, which can receive and decode a signal that is generated by superposition coding.
2. Description of the Related Art
In the case of receiving and decoding a signal that is generated by superposition coding technology, receivers in the related art perform decoding through a successive cancellation (SC) method.
The SC method is a method to successively decode and cancel superimposed signals in the order of their decoding success rates, and generally performs decoding and cancellation of an upper layer signal having high signal power first. For example, as shown in FIG. 1, the SC method may first decode a layer-1 signal, cancel the decoded layer-1 signal from a superposition coded signal (or a superposition coding signal), and then repeat the same process with respect to a layer-2 signal.
On the other hand, in the case of performing decoding through the SC method, the remaining residual signals, excluding a signal to be decoded, may act as interference signals. Accordingly, in order to reduce calculation complexity due to the interference signals, Gaussian approximation is applied to approximate the interference signals to Gaussian noises in performing the decoding process.
For example, as shown in FIG. 2, in the case of performing decoding of an uppermost layer signal, the uppermost layer signal is decoded through approximation of the remaining layer signals (i.e., layer-3 signal (upper signal) and layer-2 and layer-4 signals (lower signals)) to Gaussian noises.
However, in the case of applying the Gaussian approximation, a difference between an actual signal and the approximated signal may occur, and this may cause decoding performance to deteriorate.
In particular, in the case of applying the Gaussian approximation to a signal to which a QPSK (Quadrature Phase Shift Keying) modulation method is applied, a great difference occurs between the actual signal and the approximated signal in comparison to other high-order modulation methods. In this case, since the upper layer signal of the superposition coded signals is modulated in the QPSK method, greater performance deterioration may occur when the first signal is decoded.
Accordingly, there is a need for schemes to address the decoding performance deterioration due to the Gaussian approximation when the first signal is decoded.